Noncorrosive solution



Patented Ag. 9, 1927.

are s MICHIGAN, ASSIGNOR TO HYDRAULIC 'MOR-TON 'ROLA'ND SHERBINO, OF DETROIT, I

BRAKE COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF CALIFORNIA.

ivoncormosrva somrrrou.

No Drawing. Application filed March 19, 1926. Serial No. 96,083.

This invention relates to a solution comprising castor oil, alcohol and a neutralizing or catalytic agent such as a compound of arsenic or phosphorus soluble in alcohol,

the solution being intended primarily, al-

though not necessarily, as the fluid medium of a hydraulic braking system for automobiles.

Heretofore, it has been common practice '10 to use a solution of alcohol and castor oil in substantially equal proportions for actuating the pistons in so-called hydraulic braking systems. This solution has been used because of the fact that castor oil thus dissolved in alcohol has no detrimental effect upon rubber used for cup washers and for piping, and at the temperatures encountered in practice has a sufficiently constant viscosity for practical purposes. It has been found in practice that even chemically pure castor oil, when mixed with either ethyl or methyl alcohol brings about a gradual cor.-

rosion of the commonly used metals, such as iron, steel, brass, copper and the metals 2 found in die casting alloys. To minimize this corrosive effect, the interiors of'certainparts of the fluid braking systems have been electro-plated with cadmium, but although this retards the action, it has been found that the ,action continues to some extent,

with the result that a material which I designate as cadmium soap is formed. This soap-like material results from the contact of cadmium with castor oil in the presence of alcohol and is sufficiently insoluble in the quantity of alcohol present in the braking solution that it eventually forms a hard and obstructive precipitate of a soap-like character.

I have found that the corrosion of the above named metals is greatly decreased by the addition to the castor oil-alcohol solution of a neutralizing or catalytic agentpreferably a compound of arsenic-and that v these compounds have no detrimental effect upon the rubber of the hoses or cup washers used in the system. When the copper of the system is thus cadmium plated, and particularly when the compound added to the solution is one of arsenic, the formation ofthe product which I have termed cadmium soap" is also prevented.

Almost any of the soluble arsenic compounds have a beneficial effect, but I have found that potassium arsenite (KA O and sodium arse'nite (Na HA O,) are the most satisfactory, although comparatively good results have been obtained by the use of potassium arsenate (K A O,,) and sodium arsenate (Na AsO,,12H O).

I have found that the solution of alcohol and castor oil will dissolve about two grams of arsenic compound per gallon, and that this proportion of arsenic satisfactorily prevents corrosion and the formation of soap- 6 like material. I have also found,'however, that as small a proportion as one-half gam of arsenic compound per gallon of alcoholcastor oil mixture prevents corrosion and saponification to substantially the same degree as the saturated solution, above mentioned.

One of the forms of the above mentioned corrosion which has given rise to trouble in the operation of fluid operated vehicle 7 brakes, is the copper sulphide which forms as a result of the presence of sulphur in the rubber with which the brake solution comes in cont-act and the presence of copper in the tube which conducts the brake solution to the work cylinders. This copper sulphide forms along the interior of the copper tubing, creating a thin scale which, through vibration of the tubing, becomes dislodged and is carried by the solution into the brake cylinders where it eventually lodges between the rubber cup and the cylinder wall, causing abrasion of the rubber and leakage of the fluid.

I believe that the compound of arsenic acts as a negative -;.catalytic agent, which very materially slows down the action of the dissolved sulphur upon the copper. I believe, further, that the same negative catalytic action is responsible for the diminu- 9 tion of the corrosion of other metals which come into contact with the brake fluid.

While I prefer to use the compounds of arsenic herein mentioned, I have found that other substances also give satisfactory results in minimizing the action of the sulphur on the copper or-other metals,and especially compounds of phosphorus such as tri-sodium phosphate (Na PO,.1 2I-I O). This apparently acts as a catalytic agent 1 similar to the above described arsenic compounds. I

Although my invention has been described for use in a fluid braking system, it is equally applicable to any other system mak- 1 ,cohol and an oil ing use of a solution of castor or other oil in alcohol.

I claim: 1. A solution of castor oil in alcohol, rendered non-corrosive by the addition of an alkali metal salt including a metal'of the arsenic group.

non-corrosive solution containing substantially equal parts of castor oil and alcohol, rendered inert and non-corrosive by the addition of a small proportion of an arsenicsalt soluble in said solution 3. A non-corrosive solution com risin alcohol .and castor oil containing su stantially one gram of an alkali metal arsenic compound per gallon of solution.

4. A non-corrosive brake fluid, containing equal parts of alcohol and castor oil, and a soluble quantity of potassium arsenite.

5. A non-corrosive small quantity of an alkali metal arsenic salt.

I sion of the metal by the 6. The combination with a liquid medium, comprising a castor. oil and alcohol solution in contact with a metal and vulcanized rubber, of an alkali metal arsenic compound held in solution by the medium.

7. A liquid medium for fluid actuated braking-systems which comprise metal and sulphur-containing vulcanized rubber in contact with the medium, the medium comprising a solution of castor oil and alcohol with a small portion of an arsenic salt in solution therewith for minimizing the corrosulphur.

v 8. In a fluid system exposedboth to co per and to sulphur-containing vulcanized ru ber,

solution, containing al-. soluble in alcohol and a sulphur, of means for minimizing the corrosion' of metallic copper with which the solution comes into contact, comprising a small portion of an arsenic salt held in the solution.

11. In a fluid system ex osed both to cadmium plated copper an to sulphur-containin'g vulcanized rubber, the combination therewith of a liquid medium including alcohol and castor oil, and means for preventing the formation of cadmium'soa comprising a small portion of an alkai metal arsenic compound in solution with the medium.

12. The combination with a solution of comprising a the sulphur in vulcanized castor oil in alcohol and small amounts of sulphur, of means for minimizing the corro-' sion of metallic copper with which the solution comes into contact, comprising a small portion of an arsenite of an alkali metal held in the solution.

In witnesswhereof, I hereunto subscribe my name this 2nd day of March, 1926.

MORTON ROLAND SHERBINO. 

